Shimano’s Dura-Ace is the most influential group in the world. Not only is it the benchmark for drivetrain performance, Shimano’s size and influence mean that what happens with Dura-Ace can literally change the market.

Here's your Dura Ace 9100-series number decoder to help you keep the parts straight:

R9100: this code is applied to the group's foundational components like the bottom bracket, cranks, chain, and cassette, as well as the mechanical-shift derailleurs, and the STI levers for mechanical shifting and cable-actuated (rim) brakes.

R9170: this code is on the STI levers for Di2 shifting and hydraulic disc brakes, as well as the Dura Ace disc calipers

The group remains 11-speed, but the black mirror finish is new. The R9150/9170 Di2 components are almost entirely cross-compatible with existing 9070 Di2—the front derailleur is the exception. The R9100/9120 mechanical parts are also mostly cross-compatible with R9000, except the front derailleur.

Disc Brakes
While Shimano has offered discs for road previously, they were non-series components. With R9100-series, disc brakes are officially incorporated into Dura-Ace for mechanical and Di2 shifting.

The R9170 hydraulic-braking hoods are smaller than Shimano's the non-series ST-R785–Shimano's first STI lever for Di2 shifting/hydraulic brakes–and the 9170 hoods have almost exactly the same dimensions as the 9150 hoods for rim brakes. For R9120 mechanical shifting, the hydraulic hoods are smaller than Shimano’s previous mechanical shift/hydraulic brake design. However, because of the size of the mechanical shift mechanism, they're still a little bigger than the equivalent hoods for rim brakes.

Matt Phillips

The RT-900 rotor is new and quite radical-looking. An evolution of Shimano’s existing three-layer ICETech rotor—steel braking surfaces with aluminum core—the new rotor greatly extends the aluminum core fins for increased heat dissipation. The new rotors will be offered in 160 and 140mm.

Matt Phillips

Other than finish, the calipers greatly resemble Shimano’s existing 805 flat-mount calipers, though some materials change to drop some weight, according to Shimano representatives. The Dura-Ace calipers are only offered for flat mount.

The new Dura-Ace crank is also updated to reflect the embrace of disc brakes. The rings were reprofiled so the crank maintains proper shifting performance with 135mm spaced disc hubs and stays as short as 410mm.

Power Meter
With power meters exploding in popularity among enthusiast riders, and the devices near-universal use by racers, it’s little surprise that Shimano will offer a Dura-Ace power meter crank.

It’s one of the most integrated-looking power meters available, with little to give away its presence, but it does incorporate independent left and right power meters, which are hardwired together.

A single battery, housed in the crank's axle, powers both arms. It’s charged through a magnetic charging port. The battery is not user-serviceable, and the crank must be sent to Shimano for battery replacement.

The system has two radios: Bluetooth LE, for firmware updates and settings (via Shimano’s eTube app), and ANT+ for communicating with head units. The chainrings may be changed without affecting the measurement.

Claimed accuracy is +/- two percent.

No physical sample of the power meter was shown, but it has been seen on Shimano-sponsored team bikes.

Wide-Range Cassette
Shimano will offer an 11-30 cassette for Dura-Ace, in addition to its traditional close-ratio sizes. However, instead of offering one derailleur cage length for close-ratio cassettes, and one for wide-range cassettes—like Shimano does with Ultegra, and like SRAM and Campagnolo—both mechanical and Di2 Dura-Ace rear derailleurs will be offered in one mid-length cage that's compatible with all cassettes. This means riders can switch cassettes based on terrain without needing a new rear derailleur.

Matt Phillips

Outside of the new 11-30, 9100's cassettes are little changed from Dura Ace 9000: there isn't even a tooth profile change. Like the 9000 cassettes, the 9100 cassettes' first five cogs are made of titanium. Sizes offered are 11-25, 11-28, 11-30, 12-25, and 12-28.

New Rear Derailleur Design
The R9100 rear derailleurs borrow the Shadow design used by Shimano’s mountain bike components. The Shadow design tucks the rear derailleur under the stay and cassette, for greater protection from crashes.

Matt Phillips

The Shadow design mounts to the frame with a short link. Like Shimano’s mountain bike rear derailleurs, this link can be eliminated with a different hanger and “direct-mounted” to the frame, which offers a stiffer interface for improved shifting, company representatives claim.

Matt Phillips

According to Shimano representatives, the Shadow design also allows for easier wheel changes because it moves the derailleur out of the way of the dropout—something that's particularly advantageous with thru axles and wider tires.

Cranks
The new cranks incorporate the same hollow-forged aluminum asymmetrical four-arm design as its predecessor. However, the new crank is slightly lighter (621 vs 629 grams) with no stiffness loss. The spider arms are wider than before, so chainrings are not cross-compatible between the 9000 and 9100 cranks.

Matt Phillips

As mentioned above, the new crank has re-profiled chainrings to function properly with 135mm rear hub spacing for disc brakes and chain stays as short as 410mm.

The cranks are offered in 165, 167.5, 170, 172.5, 175, 177.5, and 180mm lengths and with 50-34t, 52-36t, 53-39t, 54-42t, or 55-42t rings.

Syncro Shifting
Borrowing another feature from Shimano’s Di2 mountain bike groups, R9100 has a synchronized-shifting, which is enabled through the Shimano E-TUBE app. When enabled, shifting the front chainrings will trigger an automatic rear derailleur recovery shift of one or two cogs to prevent large cadence changes.

Di2 STI levers
Shimano has updated the Di2 hood and lever shape. The lever shape and hood contour is new, and the main button that's closest to the bar has been extended and is easier to reach from both hoods and drops, says Shimano.

Matt Phillips

The mode button hidden in the top of the Di2 levers has been repositioned closer to the front of the hood. Its function can be customized thru Shimano's E-TUBE app, and may be used for shifting. This button was not present in the ST-R785 Di2/hydraulic levers, but Shimano has added it to the 9170 STI levers.

Matt Phillips

The switches are improved as well, with a more distinctive click.

As mentioned above, the Di2 hoods for hydraulic and rim brakes are almost identical in size and shape.

Di2 Battery
The memory on the existing Di2 battery was maxed out, so the new Di2 battery has expanded memory. This expanded memory is required for syncro shifting and wireless connectivity.

With this battery, existing 9070 Di2 can be upgraded via firmware update with syncro shift and wireless dongle compatibility. This battery, shared with XT Di2, is shipping in July.

Di2 eTube
Shimano has developed a new integrated junction box to clean up the look of Di2 box. Like the existing “Junction-A” box, the new box incorporates a charging port, mode switch, and status LEDs, but is shaped to be integrated into the frame or used as a bar-plug. Shimano’s PRO components division has already developed handlebars with cable ports to accept the integrated box.

Matt Phillips

Outside of the new integrated box, R9150/R9170 can be used with Shimano’s existing five port external junction-A box, and a new three port external junction-A box is in the works. The junction-B box, usually hidden in the frame, is unchanged.

Replacing the D-Fly wireless unit is a new inline wireless dongle. Like D-Fly, this will transmit battery and gear info via ANT+ to a head unit (like a Garmin Edge 520), but also has a Bluetooth LE radio, allowing wireless firmware updates and customization of shifting parameters from Shimano's app.

Shimano has also developed new wiring options–a y-connector is one example–to help clean up and accommodate aero and integrated front ends,

Rim Brakes
The R9100 rim brakes are “sleeker and more aerodynamic” than 9000, yet Shimano has also increased tire clearance to, officially, 28mm. A small brake booster is hidden between the pivots to improve "feel" by 43 percent, the company’s documents claim. The brake's quick-release lever was changed so, when closed, follows the contour of the caliper, for a sleeker appearance, and some aerodynamic benefit, according to a Shimano representative.

Matt Phillips

The direct-mount rim brakes were redesigned as well. Besides cosmetics, they’re sleeker and have added tire clearance (officially up to 28mm). Like the center-mount caliper, the direct-mount rim brakes incorporate a brake booster.

Matt Phillips

Mechanical STI Levers
The 9100 mechanical-shifting mechanism receives updates to reduce throw, and make it even lighter action than already-light R9000. The R9100 STI hoods are smaller than R9000's hoods, and almost the same size as the R9150 Di2 hoods. Repeating the info above: the R9120 STI hoods are also smaller than Shimano’s previous mechanical shift/hydraulic brake design, however, they remain larger than the R9100 STI hoods for rim brakes.

Matt Phillips

Mechanical Derailleurs
The biggest update to the mechanical derailleurs can be found in the front derailleur. The long-arm design is gone in favor of a smaller design that–in response to the trend towards wider tires–provides more clearance. Despite the new design, Shimano’s representatives state there is no change in shift effort. The front derailleur also incorporates an integrated cable tension adjustment, eliminating the need for an in-line adjuster, or one built into the frame.

Matt Phillips

Like the Di2 rear derailleur, the mechanical rear derailleur gets the Shadow design, and one cage length compatible with all cassettes from 11-23 to 11-30.

Weights
According to Shimano’s claimed weights, the R9150 Di2 group for rim brake is 2051 grams, 50 grams lighter than 9070. The R9100 mechanical group for rim brake is 2097 grams, four grams lighter than R9000

For disc brakes, Shimano is claiming a group weight of 2389 grams for the 9170 group, and 2445 grams for the 9120 mechanical shifting group.

Availability
According to Shimano, the 9100 mechancial/rim brake parts will be offered first, arriving in September 2016. 9150 Di2/rim brake parts come next, in January 2017. The 9120 and 9170 disc options for mechancial and electronic shifting come in March of 2017. TT/triathlon parts arrive in March 2017. Finally, a hydraulic-brake system for TT/tri will arrive in June of 2017.

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